Toy building block



FIG. 1 is a top plan view of a toy building block showing our new design;

FIG. 2 is a bottom plan view;

FIG. 3 is a front elevational view;

FIG. 4 is a side elevational view; and

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a toy building block, substantially as shown and described. 